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EXPERT SYSTEMS AND SOLUTIONS
Email: [email protected]
[email protected]
Cell: 9952749533www.researchprojects.info
PAIYANOOR, OMR, CHENNAI
Call For Research Projects Final
year students of B.E in EEE, ECE, EI,
M.E (Power Systems), M.E (Applied
Electronics), M.E (Power Electronics)
Ph.D Electrical and Electronics.
Students can assemble their hardware in our
Research labs. Experts will be guiding theprojects.
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MEASUREMENT ANDINSTRUMENTATION
By:
G.RAMA KRISHNA PRABU M.E.,SENIOR LECTURER
V.M.K.V ENGINEERING COLLEGE
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Gross Errors It occur due to carelessness or lack of experience
of a
human begin, due to incorrect adjustments of instruments
The errors cannot be treated mathematically
The errors are also called personal errors.Ways to minimize
gross errors:
Taking great care while taking the reading, recording the
reading &calculating the result
At least three or more readings must be taken * preferablyby
different persons.
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Systematic errors:
A constant uniform deviation of the operation of an instrument
isknown as a Systematic error
The Systematic errors are mainly due to the short comings of
the
instrument & the characteristics of the material used in the
instrument,
such as defective or worn parts, ageing effects, environmental
effects,
etc.
Types of Systematic errors:
i) Instrumental errors
ii) Environmental errors
iii) Observational errors
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Ways to minimize this error:
Selecting a proper instrument and planning and proper procedure
for
the measurement
Applying the proper correction factors
Calibrating the instrument carefully against a standard
b) Misuse of instruments:
A good instrument if used in abnormal way gives misleading
results.
Poor initial adjustment, Improper zero setting, using leads of
high resistance etc., arethe examples of misusing a good
instrument.
Such things do not cause the permanent damage to the instruments
but definitely causethe serious errors.
C) Loading effects : Loading effects due to improper way of
using the instrument cause the serious errors.
The best example of such loading effect error is connecting a
well
calibrated volt meter across the two points of high resistance
circuit.
The same volt meter connected in a low resistance circuit gives
accurate reading. Ways
to minimize this error:
Thus the errors due to the loading effect can be avoided by
using an instrument
intelligently and correctly.
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Environmental Errors: These errors are due to the conditions
external to the measuring instrument.
The various factors resulting these environmental errors are
temperature changes, pressurechanges, thermal emf, and ageing of
equipment and frequency sensitivity of aninstrument.
Ways to minimize this error:
i) Using the proper correction factors and using the
information
supplied by the manufacturer of the instrument
ii) Using the arrangement which will keep the surrounding
conditions
constant
iii) Reducing the effect of dust , humidity on the components
byhermetically sealing the components in the instruments
iv) The effects of external fields can be minimized by using
the
magnetic or electro static shields or screens
v) Using the equipment which is immune to such environmental
effects.
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ObservationalErrors:
These are the errors introduced by the observer.
These are many sources of observational errors such as parallax
error whilereading a meter, wrong scale selection, etc.
Ways to minimize this error : To eliminate such errors one
should use the instruments with mirrors, knife
edged pointers, etc.,
Random Errors:
Some errors still result, though the systematic and instrumental
errors
are reduced or at least accounted such errors are unknown and
hencethe errors are called random errors.
Ways to minimize this error
The only way to reduce these errors is by increasing the number
of
observations and using the statistical methods to obtain the
best
approximation of the reading.
